Conventionally, a wire rod of a Nb-Ge metallic material (for example, Nb.sub.3 Ge) and the like is used as a superconducting material. However, it is limited to such uses as for a superconducting magnet.
In addition, in recent years ceramic materials which exhibit superconducting properties are known. However, these are also in tablet form and as yet there has been no development of superconducting materials in thin film form.
Methods by which thin film is produced by patterning, using photolithographic techniques, and the use of this thin film as one part of the connecting wiring of a semiconductor device are also completely unknown.
There has also been no consideration on reliability at connections or contacts between the semiconductor device and the oxide superconducting material.
The development of more and more refined semiconductor integrated circuits with high speed action has in recent years become a necessity. Also, along with this refinement a drop in reliability from the heat generated in the semiconductor element and also a reduction in activation speed in the heated parts has become a problem.
When the foregoing semiconductor elements are cooled to the temperature of liquid nitrogen, the mobility of the electrons or the holes can be increased 3 or 4 times. In addition, it becomes possible to increase the frequency of operation of the device.
In order to eliminate such problems, the inventor of the present invention previously invented a superconducting semiconductor device as described in the copending Patent Applications NO. SHO-62-053724 and SHO-63-053725, which were entitled "Superconducting Semiconductor Device" and filed on Mar. 9, 1987. In such a superconducting semiconductor device, the lead wire is made of an oxide superconducting material. In a material of this type, after the material is formed on the surface to be formed, oxidation must be carried out over a long period in an oxidizing atmosphere. For this reason, the oxidizing reaction occurs simultaneously at the contact section with the semiconductor device provided on its bottom side. It should be noted that the oxide material of that semiconductor material is silicon oxide which is an insulating material.
On the other hand, the superconducting material is a copper compound. If this copper becomes diffused throughout the semiconductor through the contact section, recombination center would be created because copper is an interstitial type atom.
Accordingly, improvement in the heat resistant and oxidation resistant capabilities of this contact section is considered to be extremely important.